IntrinsicallySizedTableView.swift

//
//  ViewController.swift
//  Table
//
//  Created by Kyle Bashour on 1/21/20.
//  Copyright © 2020 Kyle Bashour. All rights reserved.
//

import UIKit

class ViewController: UITableViewController {

    override func numberOfSections(in tableView: UITableView) -> Int {
        return 10
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 1
    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = TableTableViewCell()
        return cell
    }

    override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
        return "Section \(section)"
    }
}

class IntrinsicallySizedTableView: UITableView, UITableViewDataSource {

    /// This is the trick - tells autolayout what size the table view should be
    override var intrinsicContentSize: CGSize {
        contentSize
    }

    /// And this ensures whenever the table view reloads/changes the intrinsic size is updated
    override func layoutSubviews() {
        super.layoutSubviews()
        invalidateIntrinsicContentSize()
    }

    init() {
        super.init(frame: .zero, style: .plain)
        dataSource = self
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 10
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = UITableViewCell()
        cell.textLabel?.text = "Row \(indexPath.row)"
        return cell
    }
}

class TableTableViewCell: UITableViewCell {
    override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)

        let table = IntrinsicallySizedTableView()
        table.translatesAutoresizingMaskIntoConstraints = false

        contentView.addSubview(table)

        NSLayoutConstraint.activate([
            table.topAnchor.constraint(equalTo: contentView.topAnchor),
            table.bottomAnchor.constraint(equalTo: contentView.bottomAnchor),
            table.leadingAnchor.constraint(equalTo: contentView.leadingAnchor),
            table.trailingAnchor.constraint(equalTo: contentView.trailingAnchor),
        ])
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}